They stood together in the garden of Downing Street and swapped compliments.

"We have a shared language, we have a shared outlook on many of the issues which face us. We are determined too to share our ideas, our expertise and our commitment to a new era of co-operation and of understanding," the British premier said.

Bill Clinton is looking forward to some serious policy discussion

The significance of this political union was not lost on the Washington and Westminster press corps.

Fred Barnes - journalist, and archetypal Washington insider - says the two leaders are, in many ways, direct parallels. "People in the political community in the United States who've watched Tony Blair very carefully see him in some ways as a newer, and even better version of Bill Clinton.

"Now what has Bill Clinton done? He has certainly moved his party, the Democratic Party, to the centre, somewhat. And Tony Blair has done it even more dramatically, bringing the Labour Party to the centre.

"Both are guys with the gift of the gab we haven't seen in an awful long time. And both have tried to bring - at least rhetorically - a moral dimension to politics."

Questions about Monica Lewinsky

At some stage on the trip Mr Blair will inevitably face questions about the sexual scandal which has rocked the White House.

Tony Blair

Publicly, and indeed privately, Tony Blair's advisers vigorously insist they are relaxed about the moral haze hanging over the White House.

Journalists have been told in briefings this trip will be dominated by lots of long and serious policy discussions. But come Thursday's joint press conference, It will be difficult for President Clinton, and perhaps even Mr Blair, to duck the sex questions.

What the White House will want - and probably get - is Tony Blair saying that media obsessions are irrelevant. He is likely to emphasise that President Clinton is a man who concentrates on the "big picture".

It is the sort of intervention that will guarantee Mr Blair plenty of exposure on American news networks.

But for three days this week, Tony Blair and Bill Clinton will attempt to push what they regard as a more serious agenda.

There will be talk of both men forging a "third way" in politics - centre-left talk for welfare reform and measured intervention in the free market. And conversation will inevitably drift towards Iraq and Northern Ireland.